Method of treatment

ABSTRACT

The present disclosure teaches the treatment of a blood pathology, such as a blood pathology associated with impaired hemoglobin synthesis including the treatment of β-thalassemia or a related hemoglobinopathy. An RNA molecule such as a short interfering RNA or a hairpin RNA which targets an mRNA species encoding α-globin is administered to a subject to reduce the amount of α-globin produced to non-zero levels and ameliorate the effects of an α- and β-globin chain imbalance.

FILING DATA

This application is associated with and claims priority from AustralianProvisional Patent Application No. 2010905599, filed on 22 Dec. 2010,entitled “A method of treatment”, the entire contents of which, areincorporated herein by reference.

FIELD

The present disclosure teaches the treatment of a blood pathology, suchas a blood pathology associated with impaired hemoglobin synthesisincluding the treatment of β-thalassemia or a related hemoglobinopathy.

BACKGROUND

Bibliographic details of the publications referred to by author in thisspecification are collected alphabetically at the end of thedescription.

Reference to any prior art in this specification is not, and should notbe taken as, an acknowledgment or any form of suggestion that this priorart forms part of the common general knowledge in any country.

Thalassemia is an inherited autosomal recessive blood disorder caused bythe faulty synthesis of hemoglobin. This arises by one or more geneticdefects affecting synthesis of the α- or β-globin chains which make uphemoglobin.

The World Health Organization (WHO) has conservatively estimated thatapproximately 7 percent of the world's population are carriers ofvarious types of hemoglobinopathies, with an estimated 300,000 severelyaffected patients born worldwide each year. Although thalassemia is mostcommon in Mediterranean, Middle Eastern, African and Asian populations(Olivieri (1999) N Engl J Med 341:99-109; Thein (2005)Hematology:31-37), the ever rising rates of population migration meanthis condition is encountered with increasing frequency in many parts ofthe world, including Northern Europe, North America and Australia.Thalassemia is fatal if left untreated and patients are dependent on aregular blood transfusion every 3-4 weeks for the rest of their lives.

There are over 200 β-globin gene mutations (Olivieri (1999) supra) whichimpair β-globin synthesis, resulting in imbalanced globin chainsynthesis and β-thalassemia. In these situations, the excess, unboundα-globin chains precipitate in erythroid progenitor cells resulting inpremature cell death, ineffective erythropoiesis and severe anemia. Thekey role of globin imbalance in contributing to thalassemia severity ismost clearly illustrated in individuals who inherit an abnormal numberof functional α-globin genes along with β-globin mutations. Individualswho co-inherit α-thalassemia with homozygous β-thalassemia have animproved phenotype and suffer less severe anemia than if either set ofmutations was inherited alone (Camaschella et al. (1995) Am J Hematol48:82-87; Cao et al (1991) Am J Pediatr Hematol Oncol. 13:179-188;Kanavakis et al. (2004) Blood Cells Mol Dis 32:319-324; Schrier (2002)Curr Opin Hematol 9:123-126; Thein (2005) Haematologica 90:649-660). Thedegree of correction is closely related to the degree to which globinchain balance has been restored (Thein et al (1984) Br J Haematol.56:333-337). One mutated copy of α-globin generally has minimal impactbut two or three mutated α-globin genes can improve β-thalassemicphenotypes significantly (Camaschella et al. (1995) supra; Cao et al.(1991) supra; Kanavakis et al. (2004) supra; Schrier (2002) supra; Thein(2005) supra). Therefore, alterations in α-globin chain synthesis canhave considerable effects on β-thalassemic phenotypes and can evenconfer transfusion independence. Given that excess production ofα-globin leads to widespread detrimental effects in β-thalassemia,reduction of α-globin synthesis would likely improve the β-thalassemicphenotype, raising the possibility of reducing α-globin expression as atherapy for β-thalassemia. The difficulty, however, is to specificallytarget α-globin gene expression.

Expression and synthesis of the α-globin and β-globin chains ofhemoglobin is balanced during normal erythropoiesis and any disruptionsin the α:β-globin synthesis ratios results in thalassemia (Olivieri(1999) supra; Thein (2005) supra). β-Thalassemia arises when α-globin issynthesized at levels exceeding the binding capacity of availableβ-globin chains, usually due to mutations affecting the β-globin locuswhich reduce β-globin expression (Schrier (1994) Annu Rev Med45:211-218). Conversely, α-thalassemia occurs due to mutations whichresult in decreased α-globin expression, leading to an excess ofβ-globin chains (Schrier (1994) supra). Reduced expression of either ofthe globin chains leads to decreased formation of functional hemoglobintetramers, yet this plays a relatively minor role in contributing to theseverely anemic phenotype characteristic of the thalassemias. Instead,it is the damage caused at the cellular level by excess, improperlypaired globin chains, which leads to premature cell death and accountsfor the majority of the pathology (Schrier (1994) supra). Excessα-globin results in the formulation of large, insoluble aggregates whichcan be visualized by light microscopy in an estimated one third ofβ-thalassemic red blood cells (RBCs) [Fessas (1963) Blood 21:21-32], andoccurs even in the earliest erythroid precursor cells (Schrier (1994)supra). These α-globin aggregates cause mechanical damage to membranestructures and trigger premature apoptosis in erythroid progenitorcells, leading to ineffective erythropoiesis (Thein (2005) supra;Kanavakis et al. (2004) supra). Furthermore, the excess α-globin isheavily oxidized (Advani et al. (1992) Blood 79:1064-1067) and eachglobin chain also carries a heme bound iron which can induce generationof reactive oxygen species (ROS) [Schrier et al. (2003) Redox Rep.8:241-245]. It is believed that the increased ROS oxidizes adjacentmembrane proteins, leading to severe membrane abnormalities and unstablecell membranes and this results ultimately in hemolysis and ungreatlyexacerbating the anemic phenotype in β-thalassemia (Advani et al. (1992)supra).

RNAi is a highly conserved, naturally occurring mechanism of genesuppression found in plant, yeast and mammalian cells, which can bemediated by naturally occurring or synthetic short interfering RNAs(siRNA) [Harmon (2002) Nature 418:244-251]. In mammalian cells, RNAi canbe induced using dsRNA of 19-21 bp with characteristic two nucleotide 3′overhangs and 5′ phosphate groups. These are incorporated into an RNAinduced silencing complex (RISC) and used as a template for cleavage ofendogenous mRNA. Since targeting is dependent mainly on Watson-Crickbase-pairing, it is theoretically possible to utilize this pathway toreduce expression of any gene in a sequence-specific manner.

Sarakul et al. (2008) Biochemical and Biosphysical ResearchCommunication 369:935-938 disclosed the use of siRNA at a specificregion of Exon2 of the α-globin gene locus. However, other target siteswithin the gene were ineffective in reducing expression. Chinese PatentApplication No. 100567490 (CN 100567490) also used siRNA to targetspecific sites with variable effectiveness. These sites were defined α2and α3 (referred to herein as “CNα2” and “CNα3”, respectively). CNα3targets codons 127 to 133 which is SEQ ID NO:3 in Sarakul et al. (2008)supra. The latter authors stated that only one sequence (SEQ ID NO:1,targeting codons 41 to 47 in Exon2) had any effect. Hence, there isclearly inconsistency between the data by Sarakul et al. (2008) supraand CN100567490. This highlights the difficulty in designing effectivesiRNA molecules. The present disclosure included siRNA encoding SEQ IDNO:1, (targeting codons 41 to 47 in Exon2) as a control (referred to asHs-siα5) and found that this siRNA was the least effective in reducingalpha-globin expression compared to all other siRNA tested. Alsodemonstrating that siRNA targeting other regions not anticipated bySarakul et al. (2008) supra and CN100567490 are potentially moreeffective in reducing α-globin.

In order to assess the feasibility of RNAi-mediated therapy, a mousemodel has been developed. The most well characterized is theheterozygous β-globin knockout (β-KO) model (Yang et al. (1995) ProcNatl Acad Sci USA 92:11608-11612), which displays distinct hematologicalabnormalities consistent with β-thalassemia (wide variations of red celldistribution width (RDWs), significant reductions in hemoglobin (Hb) andhematocrit (HCT) levels) [Yang et al. (1995) supra; Beauchemin et al.(2004) J Biol chem. 279:19471-19480; Vadolas et al. (2005) BiochimBiophys Acta 1728:150-162). In order to assess the effects of reducedα-globin expression in β-thalassemic mice, heterozygous α-globinknockout mice (α-KO) were crossed with thalassemic β-KO mice (Beaucheminet al. (2004) supra; Al-Hasani et al. (2004) Transgenic Res 13:235-243;Paszty et al. (1995) Nat Genet 11:33-39). The resultant doubleheterozygous (DH) α-KO/β-KO progeny expressed reduced, but balanced,levels of both α-globin and β-globin and displayed a normal range ofRDWs with Hb and HCT almost completely restored to wild type (WT)levels. Furthermore, the reduced drive for extramedullary erythropoiesiscombined with reduced clearance of damaged RBC, resulted in a markedreduction in spleen size indistinguishable from those found in WT mice.

Whilst intuitively there are benefits of reducing α-globin expression inthe context of β-thalassemia, there have been no reported substantialreductions of α-globin using methods which are conducive to therapy inhumans. An siRNA approach was investigated to mediate reductions inα-globin expression in mice. One highly effective siRNA sequence (siα4),located in the 3′ untranslated region, was demonstrated to reduceα-globin expression in hemoglobinized murine erythroleukemic (MEL) cellsby approximately 65% at both the RNA and the protein levels (Voon et al.(2008) Haematologica 93:1238-1242). The efficacy of siα4 was furtherconfirmed by testing this sequence in primary cultures of erythropoieticprogenitor cells

There is a need to use gene silencing technology to greater effect totreat β-thalassemia and related conditions arising from an excess amountof α-globin in humans.

SUMMARY

The present disclosure teaches a method for treating β-thalassemia or arelated hemoglobinopathy associated with an excess of α-globin inhumans. Related conditions include HbE disease and sickle cell disease(SCD). The method enabled herein targets the α-globin genetic locus toreduce its expression thereby reducing levels of the α-globin chain.Reference to the human α-globin genetic locus includes HBA1 (SEQ IDNO:41) and HBA2 (SEQ ID NO:604). This in turn corrects or at leastimproves or reduces the α:β-globin ratio imbalance which leads to anamelioration of the symptoms or underlying cause of β-thalassemia. In anembodiment, the agent is an RNA such as a single or double (duplex)short, interfering RNA (siRNA) oligonucleotide or a hairpin form thereofor a chemically modified or synthetic or mimetic form thereof whichtargets a mRNA species transcribed from the α-globin genetic locus at asite selected from the 5′ untranslated region (5′-UTR), Exon1, Exon3 andthe 3′-UTR or a boundary region between. The oligonucleotide may besynthetically derived or produced by expression of a DNA sequence in anexpression vector such as a Lentiviral vector. Generally,down-regulation of the α-globin genetic locus is mediated via RNAi. Inan embodiment, the ratios of α-globin and β-globin are improved to nearnormal levels. In an embodiment, the RNAi approach is used inconjunction with gene therapy to restore normal or near normal β-globinlevels.

The present specification is instructional on a gene silencing approachto reduce expression of the α-globin genetic locus to non-zeroexpression levels which means expression of the α-globin genetic locusor levels of α-globin protein is from about 30% to 95% of the levels ina cell from a non-β-thalassemic subject (“normal control”). Examples ofRNA molecules are those which target or comprise a nucleotide sequenceof α-globin mRNA selected from SEQ ID NOs:25 and 26 (sense andanti-sense Hs-siα1), 27 and 28 (sense and antisense Hs-siα2), 29 and 30(sense and antisense Hs-siα3), 31 and 32 (sense and antisense Hs-siα4).However, any site within the 5′-UTR, Exon1, Exon3 or the 3′-UTR orboundary regions inbetween and which results in a reduction in α-globinlevels may be targeted.

Examples of mimetics include peptide-oligonucleotide chimeras referredto as a peptide oligonucleotide. Examples of other modified formsinclude branched oligonucleotides hairpin oligonucleotides and syntheticoligonucleotide comprising chemically modified bases or bonds betweenbases. Hairpin RNA species are particularly useful in the practice ofthe present method.

In an embodiment, the agent is an siRNA oligonucleotide comprising amolecule of from about 15 to about 50 bp in length of HBA1 and/or HBA2mRNA. Exemplary oligonucleotides target a region on α-globin mRNAselected from SEQ ID NO:42 to SEQ ID NO:603 and SEQ ID NO:605 to SEQ IDNO:1212. Whilst the 15mer oligonucleotides are exemplary targetsequences, the present disclosure teaches oligonucleotides from 15 to 50nucleotides in length which target or comprise a sequence comprising asequence set forth in one of the 15mers. Particular examples of targetsinclude SEQ ID NO:25, 26, 27, 28, 29, 30, 31 and 32. The RNAi-mediatedsilencing may also employ RNA species comprising a nucleotide sequenceselected from SEQ ID NO:25, 26, 27, 27, 28, 29, 30, 31 and 32.

The method contemplated herein does not extend to the specific targetsite Hs-siα5 disclosed by Sarakul et al (2008) supra and CN 100567490and sites α2 and α3 also disclosed by the Chinese patent application.The Hs-siα5 is used herein as a control.

Enabled herein is a method for treating a human subject withβ-thalassemia or a related hemoglobinopathy, the method comprisingadministering to the subject an amount of an agent effective to reduceexpression of the α-globin genetic locus thereby reducing levels ofα-globin and ameliorating the effects of an α- and β-globin chainimbalance. Reducing expression of the α-globin genetic sequence includestargeting α-globin mRNA. The method may be practices alone or incombination within gene therapy to introduce a functionalβ-globin-encoding nucleic acid molecule.

Further taught herein is the use of an agent which reduces expression ofthe α-globin genetic locus in the manufacture of a medicament in thetreatment of β-thalassemia or a related hemoglobinopathy in a subject.

The present disclosure provides a method for treating a human subjectwith β-thalassemia or a related hemoglobinopathy, the method comprisingadministering to the subject an effective amount of a RNA which targetsan mRNA species encoding α-globin at a site selected from the 5′-UTR,Exon1, Exon3 and 3′-UTR or a boundary region inbetween to thereby reducethe amount of α-globin produced to non-zero levels and ameliorate theeffects of an α- and β-globin chain imbalance.

The agents may be oligonucleotides such as an RNA species or may be acellular or viral vector capable of producing a DNA-derived orRNA-derived RNA species.

In an embodiment, an agent is provided comprising a RNA which targets anmRNA species encoding α-globin at a site selected from the 5′-UTR,Exon1, Exon3 and the 3′-UTR and a boundary region inbetween to reducethe amount of α-globin produced for use in ameliorating the symptoms ofβ-thalassemia or a related hemoglobinopathy in a subject.

In an embodiment, the RNA is an siRNA or a chemically modified ormimetic thereof. This includes a hairpin RNA species. Examples of RNAmolecules comprise or target a sequence selected from SEQ ID NO:25, 26,27, 28, 29, 30, 31 and 32. Other examples, are agents which target SEQID NO:42 to 603 or SEQ ID NO:605 to 1212 with the exception of CNα2,CNα3 and Hs-siα5.

Systems for the treatment of β-thalassemia or a related hemoglobinopathyarising from an imbalance of α-globin and β-globin chains are alsocontemplated herein. One such system taught herein the use of acombination of β-globin gene therapy and RNAi-mediated reduction inα-globin. In an example of this system, a Lentiviral (LV) vector is usedto deliver a β-globin-encoding nucleic acid molecule and RNAi sequencesto specifically target α-globin mRNA at a site selected from its 5′-UTR,Exon1, Exon3 and 3′-UTR or a boundary region inbetween. The system aimsto normalize α:β-globin ratios. Conveniently, the RNAi-encodingsequences are inserted in a 5′-UTR or 3′-UTR or intron in theβ-globin-encoding sequence.

In an embodiment, the instant disclosure teaches a RNA which targets amRNA species encoding α-globin at a site selected from the 5′-UTR,Exon1, Exon3 and the 3′-UTR and a boundary inbetween to reduce theamount of α-globin produced in the manufacture of a medicament in thetreatment of β-thalassemia or a related hemoglobinopathy in a subject.

Another aspect enabled herein is directed to a vector comprising anucleic acid molecule encoding human β-globin operably linked to apromoter and one or more second nucleic acid molecules inserted in the5′-UTR and/or 3′-UTR region and/or an intron of the β-globin-encodingnucleic acid molecule which second nucleic acid molecule encodes an RNAwhich targets an mRNA species encoding α-globin at a site selected fromthe 5′ untranslated region (5′-UTR), Exon1, Exon3 and the 3′-UTR or aboundary region inbetween. In an embodiment, the vector providestherapeutic levels of β-globin while reducing α-globin levels.

A summary of sequence identifiers used throughout the subjectspecification is provided in Table 1. Abbreviations referred to hereinare defined in Table 2.

TABLE 1 Summary of sequence identifiers  1 si-α1 sense  2 si-α1antisense  3 si-α2 sense  4 si-α2 antisense  5 si-α3 sense  6 si-α3antisense  7 si-α4 sense  8 si-α4 antisense  9 pshα1 oligo 10 pshα1oligo FWD 11 pshα1 oligo 12 pshα1 oligo REV 13 pshα2 oligo 14 pshα2oligo FWD 15 pshα2 oligo 16 pshα2 oligo REV 17 pshα3 oligo 18 pshα3oligo FWD 19 pshα3 oligo 20 pshα3 oligo REV 21 pshα4 oligo 22 pshα4oligo FWD 23 pshα4 oligo 24 pshα4 oligo REV 25 Hs_si-α1 sense 26Hs_si-α1 antisense 27 Hs_si-α2 sense 28 Hs_siα2 antisense 29 Hs_si-α3sense 30 Hs_si-α3 antisense 31 Hs_si-α4 sense 32 Hs_si-α4-antisense 33Hs_si-α5 sense 34 Hs_si-α5 antisense 35 Stealth si-α1 sense 36 Stealthsi-α1 antisense 37 Stealth si-α2 sense 38 Stealth si-α2 antisense 39Stealth si-α3 sense 40 Stealth si-α3 antisense 41 Nucleotide sequence ofhemoglobin α1 (HBA1) mRNA 42 to 601 15mer sense oligonucleotides whichrepresent targets on HBA1 mRNA¹ 602  Nucleotide sequence of hemoglobina1 (HBA2) mRNA 603-1210 15mer sense oligonucleotides which representtargets on HBA2 mRNA² 1211  Complement in same direction after U to Tconversion - HBA1 ¹Target sequences based on HBA1 (NM_000558.3). ²Targetsequences based on HBA2 (NM_000517.4).Insofar as the target is mRNA, T nucleotides are U nucleotides. Both RNAand DNA sequences are encompassed herein.

TABLE 2 Abbreviations α-KO α-Globin knock-out genotype β-KO β-globinknock-out genotype CNα2 Target site disclosed in Chinese PatentApplication No. 100567490 CNα3 Target site disclosed in Chinese PatentApplication No. 100567490 DCFH 2,7-Dichlorfluorescein DH Doubleheterozygous FBE Full blood examination FCS Fetal calf serum HbHemoglobin HBA Hemoglobin α-globin. Includes HBA1 and HBA2. HCTHematocrit LTR Long term repeat LV Lentiviral vector LVβ Leniviralvector comprising nucleic acid encoding β-globin MEL cells Murineerythroleukemic cells Retic Reticulocyte RBC Red blood cell RDW Red celldistribution width RISC RNA induced silencing complex ROS Reactiveoxygen species RRE Rev-responsive element SA Splicing acceptor SDSplicing donor SIN Self inactivating shRNA Short hairpin RNA siRNAShort, interfering RNA siα1, siα2 siRNA's targeting the 5′ end region ofthe human α-globin gene siα3, siα4 siRNA's targeting the 3′ end regionof the human α-globin gene siα5 siRNA targeting Exon2 of the humanα-globin gene WT Wild-type

BRIEF DESCRIPTION OF THE FIGURES

Some figures contain color representations or entities. Colorphotographs are available from the Patentee upon request or from anappropriate Patent Office. A fee may be imposed if obtained from aPatent Office.

FIG. 1 is a graphical representations showing the restoration of globinbalance in primary erythropoietic cells from heterozygous β-KO mice. (A)Relative α:β-globin RNA ratios in cultured primary erythroid progenitorcells from (i) WT (wild type) and heterozygous β-KO (knock out) and (ii)heterozygous β-KO cells treated with 10 μg, 5 μg or 1 μg of siα4 or ansiLuc (luciferase) irrelevant control. (B) Relative levels of ROS(reactive oxygen species) in cultured primary erythroid progenitor cellsfrom (i) WT and heterozygous β-KO and (ii) heterozygous β-KO cellstreated with 10 μg, 5 μg or 1 μg of siα4 or an siLuc irrelevant control:All values shown represent the mean average of at least threeindependent experiments±standard deviation.

FIG. 2A is a schematic representation of dominant human α2-globin mRNAand siRNA binding sites. The human α2 and α1 globin genes are identicalthrough the coding regions and differ only slightly in the UTRs(untranslated regions) so all siRNA sequences except Hs-siα4 target bothα-globin genes. Standard siRNAs designed using Qiagen algorithms arerepresented in blue and a published sequence, Hs-siα5, is represented ingreen. The modified, 25-mer Stealth sequences are represented in red.The equivalent human homologs of previously tested murine siRNA.sequences have been indicated in grey. FIG. 2B provides the nucleotidesequence (coding and non-coding) of HBA2 (NM_(—)000517.4) showinglocation of various human and murine target siRNAs. CNα2 and CNα3 referto the sequences disclosed in CN 100567490.

FIG. 3 is a graphical representation showing relative α-globin mRNAexpression in K562 cells 24 and 48 hours post electroporation withvarious siRNAs targeting human α-globin. Relative α-globin RNAexpression levels were detected by real-time PCR 24 and 48 hours postelectroporation with 1 μg of various siRNA sequences targeted toα-globin. Relative expression of α-globin was calculated by normalizingto expression levels in mock electroporated K562 cells using β-actinexpression as an RNA loading control. An siRNA sequence targetingluciferase (siLuc) was included in all experiments as an irrelevantcontrol. Values represent the mean average of at least three independentexperiments±SD.

FIG. 4 is a graphical representation showing relative α-globin mRNAexpression in K562 cells 24 and 48 hours post electroporation withvarious siRNAs targeting human α-globin. Relative α-globin RNAexpression levels were detected by real-time PCR 24 and 48 hours postelectroporation with 500 ng of various siRNA sequences targeted toα-globin. Relative expression of α-globin was calculated by normalizingto expression levels in mock electroporated K562 cells using β-actinexpression as an RNA loading control. Values represent the mean averageof at least three independent experiments±SD.

FIG. 5 is a diagrammatic representation of a lentiviral vector (LV)containing the human β0-globin gene under the control of the pol IIβ-globin promoter. Schematic representation of LV in its proviral form.LTR deleted of 400 bp in the HIV U3 region (LTR), rev-responsive element(RRE), splicing donor (SD) and splicing acceptor (SA) sites, humanβ-globin gene, β-globin promoter (p), and Dnase I-hypersensitive sitesHS2 and HS3 and β-globin LCR are shown. shRNA1 and shRNA2 representα-globin-specific shRNA insertion sites.

FIG. 6 is a diagrammatic representation of the LVβ vector. (A) LVβvector encodes an adult β-globin (β^(A(T87Q))) that forms functional Hbdistinguishable from normal Hb by HPLC. The β-globin is placed undercontrol of the human β-globin LCR, β-globin promoter (βp), and 3′β-globin enhancer. Intron-II is artificial, containing a 375 bp deletionto remove an A/T rich region that has been shown to reduce viral titre.Safety modifications include 2 stop codons in the Ψ packaging signal, a400 bp deletion in the U3 of the right HIV LTR and 2×250 bp cHS4chromatin insulators. Additional features include: central polypurinetract/DNA flap (cPPT/flap); RRE, Rev-responsive element; polypurinetract (ppt).

DETAILED DESCRIPTION

Throughout this specification, unless the context requires otherwise,the word “comprise”, or variations such as “comprises” or “comprising”,will be understood to imply the inclusion of a stated element or integeror method step or group of elements or integers or method steps but notthe exclusion of any other element or integer or group of elements orintegers or method steps.

As used in the subject specification, the singular forms “a”, “an” and“the” include plural aspects unless the context clearly dictatesotherwise. Thus, for example, reference to “medicament” includes asingle medicament, as well as two or more medicaments; reference to “anagent” includes a single agent, as well as two or more agents; referenceto “the disclosure” includes a single or multiple aspects taught herein.Aspects taught and enabled herein in the context of the treatment of ablood pathology such as β-thalassemia are encompassed by the term“invention”. All such aspects are enabled within the width of thepresent invention.

β-thalassemia is an inherited hemoglobinopathy caused by defectivesynthesis of the β-globin chain of hemoglobin. This leads to animbalance of α- and β-globin chains. Excess α-globin precipitates inerythroid progenitor cells resulting in cell death, ineffectiveerythropoiesis and severe anemia. In accordance with the teachings ofthe present disclosure, a system is developed to specifically targetexpression of the α-globin genetic locus to reduce levels of α-globin. Areduction in the levels of α-globin in β-thalassemia patients helpsreduce the imbalance of α- and β-globin chains thereby ameliorating thesymptoms of β-thalassemia in subjects. By targeting expression of theα-globin genetic locus includes specifically targeting mRNA speciesencoding α-globin. Generally, the α-globin mRNA is targeted at a siteselected from the 5′-UTR; Exon1, Exon3, the 3′-UTR and a boundary regioninbetween. The α-globin expression may be targeted alone or incombination with gene therapy to elevate β-globin levels. Reference toα-globin includes hemoglobin α-globin 1 (HBA1; SEQ ID NO:41) andhemoglobin α-globin 2 (HBA2; SEQ ID NO:604).

Accordingly, an aspect enabled herein is a method comprising the step ofadministering an agent to a human subject having or suspected of havingβ-thalassemia or a related hemoglobinopathy wherein the agent isprovided in an amount which reduces to non-zero levels the expression ofthe α-globin genetic locus thereby reducing levels of α-globin andameliorating the effects of an α- and β-globin chain imbalance.

Taught herein is a method for treating a human subject withβ-thalassemia or a related hemoglobinopathy, the method comprisingadministering to the subject an amount of an agent effective to reduceexpression of the α-globin genetic locus thereby reducing levels ofα-globin and ameliorating the effects of an α- and β-globin chainimbalance.

The present disclosure is instructional on a therapeutic system fortreating β-thalassemia or a related hemoglobinopathy in a human subject,the system comprising reducing expression of genetic material encodingthe α-globin chain of hemoglobin to thereby reduce levels of α-globin.Such a system facilitates correction, improvement or reduction in theratio of α- and β-globin chains. Reduced levels of free α-globin chainsleads to a reduction in its precipitation in erythroid progenitor cells.Reference to “β-thalassemia” includes blood pathology conditions such asa blood pathology associated with impaired haemoglobin synthesis. Suchconditions include those resulting in an α:β-globin imbalance, and whichresult in an excess of α-globin. Related hemoglobinopathies include HbEand sickle cell disease.

Further taught herein is a method of treating a blood pathologyassociated with an excess of α-globin in a subject, the methodcomprising administering to the subject an effective amount of an agentwhich reduces the level of expression of the α-globin genetic locus, thelevel being from between less than the level of expression determinedprior to intervention to a level above zero, thereby reducing α-globinproduction and normalizing α- and β-globin levels.

Taught herein is a method for treating a human subject withβ-thalassemia or a related hemoglobinopathy, the method comprisingadministering to the subject an effective amount of a RNA which targetsan mRNA species encoding α-globin at a site selected from the 5′-UTR,Exon1, Exon3, the 3′-UTR and a boundary region inbetween to therebyreduce the amount of α-globin produced to non-zero levels and amelioratethe effects of an α- and β-globin chain imbalance.

The agent may target any part of the α-globin genetic locus, includingexons, introns, 5′-UTR, 3′-UTR and boundary regions of mRNA transcribedfrom the locus. In an embodiment, the agent targets a region selectedfrom the 5′-UTR, Exon1, Exon3, 3′-UTR and any intronic region on an mRNAspecies encoding α-globin. The agent does not target the exact Hs-siα5site as disclosed by Sarakul et al, (2008) supra and in CN 100567490 orthe sites referred to in CN 100567490 as α2 and α3 (CNα2 and CNα3,respectively). The agent may target any site either side of Hs-siα5,CNα2 and CNα3 which results in reduced expression of the α-globin locus.This extends to from one nucleotide to up to 50 nucleotides 5′ or 3′ ofHs-siα5, CNα2 and/or CNα3. Hence, Exon2 of the α-globin mRNA may also betargeted but not at Hs-siα5.

The agent taught herein induces a level of gene silencing of theα-globin genetic locus. An example of such a type of agent is an agentwhich induces RNAi-mediated gene silencing. The agent may, for example,be a nucleic acid molecule or a component of RNA induced silencingcomplex (RISC). In an embodiment, the agent is an oligonucleotide insingle or double stranded form such as a single or double stranded(duplex) short, interfering RNA (siRNA) molecule or hairpin RNA whichcomprises a strand having some nucleotide identity to a nucleotidesequence within an mRNA encoded by the α-globin genetic locus such asSEQ ID NO:25, 26, 27, 28, 29, 30, 31 or 32.

In an embodiment, the agent is an siRNA of from about 15 to 50 bp inlength such as 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,47, 48, 49 or 50 bp in length or a hairpin form thereof. The agent mayextend to larger or smaller nucleic acid molecules.

The RNA may correspond to any region within the α-globin genetic locusor mRNA encoded thereby such as the 5′-UTR portion and exon thereinand/or the 3′-UTR portion. Furthermore, the siRNA may correspond to anyregion within the α-globin genetic locus or more particularly mRNAencoded thereby such as the 5′-UTR portion and/or the 3′-UTR portion.Generally, the RNA targets or comprises a nucleotide sequence selectedfrom the 5′-UTR, Exon1, Exon3, 3′-UTR or a boundary region inbetweensuch as SEQ ID NO:25 through 32.

In an embodiment, the agent is an siRNA comprising at least 15 bp whichtargets or comprises a sequence on the α-globin mRNA nucleotide sequenceselected from the list consisting of SEQ ID NO:42 through SEQ ID NO:649inclusive. It is a proviso herein that the agent does not target theexact sequence corresponding to Hs-siα5 (Sarakul et al. (2008) supra; CN100567490) (Sor the α2 and α3 sequences of CN 100567490 (CNα2 and CNα3,respectively). In an embodiment, the siRNA comprises or targets anucleotide sequence selected from SEQ ID NO:25, 26, 27, 28, 29, 30, 31and 32.

Taught herein is an agent comprising a short interfering RNA (siRNA)agent or a chemically modified or mimetic form thereof which targets anmRNA species encoding α-globin at a site selected from the 5′-UTR,Exon1, Exon3, the 3′-UTR and a boundary inbetween to reduce the amountof α-globin produced for use in ameliorating the symptoms ofβ-thalassemia or a related hemoglobinopathy in a subject.

Enabled herein is a method for treating a human subject withβ-thalassemia or a related hemoglobinopathy, the method comprisingadministering to the subject an amount of an siRNA targeting orcomprising a nucleotide sequence selected from SEQ ID NO:42 to SEQ IDNO:603 (HBA1) and SEQ ID NO:605 to SEQ ID NO:1212 (HBA2) effective todown-regulate expression of the α-globin genetic locus for a time andunder conditions sufficient to reduce levels of α-globin. Excluded fromthis embodiment is Hs-siα5, CNα2 and CNα3.

As taught herein, the expression “reducing expression of the α-globingenetic locus” means that levels of mRNA encoding α-globin or levels ofα-globin translated from the mRNA is reduced to a level of about 30% toabout 95% of the level in a cell from a subject who does not haveβ-thalassemia. It also includes reducing the level of α-globin producedto 30% -95% of the level in a cell from a subject without β-thalassemia.This is regarded as a “normal cell” or a “normal control” or“statistically determined normal levels”. By “30% to 95%” means 30, 31,32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67,68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85,86, 87, 88, 89, 90, 91, 92, 93, 94 or 95%.

Hence, it is not the aim of the instant method to totally eliminateexpression of α-globin. Rather, the intention is to reduce expression tonon-zero levels. This means to a level of from 30% to 95% relative to anormal control. In an embodiment, the level of expression of theα-globin genetic locus is reduced from less than the level prior tointervention to above zero levels, thereby reducing α-globin productionand normalizing α- and β-globin levels. In another embodiment, theexpression of the α-globin genetic locus is reduced to a level at whichequi-amounts of α-globin and β-globin are produced. In yet anotherembodiment, the RNAi agents are expressed in a 5′-UTR, 3′-UTR orintronic region of a β-globin nucleic acid molecule used in gene therapyto elevate β-globin levels.

The present disclosure teaches agents, such as oligonucleotides andsimilar species for use in reducing expression of a genetic locus ormRNA encoding human α-globin. This is accomplished by providingoligonucleotides which target or comprise at least a portion of anucleotide sequence corresponding to α-globin mRNA. By “target” includesa sequence which is complementary to the mRNA sequence to facilitatecomplementary nucleotide pair binding. Hence, the oligonucleotideencompasses RNA encoding all or a portion of α-globin includingpre-mRNA. In an embodiment, the agent herein induces gene silencingmechanisms such as RNAi-medicated gene silencing. The term “genesilencing” does not necessarily mean inducing zero expression but alevel of expression from greater than zero expression to a level lessthan the level prior to intervention.

Agents taught herein include sense oligomeric compounds, senseoligonucleotides, alternate splicers, primers, probes, and otheroligomeric compounds which comprise a nucleotide sequence havingidentity to at least a portion of mRNA encoding α-globin orcomplementary thereto. As such, these compounds may be introduced in theform of single-stranded, double-stranded, circular or hairpin oligomericcompounds and may contain structural elements such as internal orterminal bulges or loops as well as branches. Once introduced to a cell,the agents of the present invention may elicit the action of one or moreenzymes or structural proteins or complexes to effect modification ofthe α-globin mRNA or α-globin genetic locus. An example of such acomplex is RISC.

When in oligomeric form, the agent may be single-stranded senseoligonucleotide or double-stranded (duplex) structures, such asdouble-stranded RNA (dsRNA) molecules or may be chemical or synthetic ormimetic forms thereof. A chemically modified form includes branched andhairpin oligonucleotides. The oligomer may be synthetically produced orderived by expression of DNA or an RNA vector system to generate shorthairpin loops. In one embodiment, the DNA or RNA system can generateshort hairpin RNA that specifically targets the reduction in expressionof α-globin.

In the context of the method taught herein, the term “oligonucleotide”refers to an oligomer or polymer of ribonucleic acid (RNA) or mimetics,chimeras, analogs and homologs thereof. This term includesoligonucleotides composed of naturally occurring nucleobases, sugars andcovalent internucleoside (backbone) linkages as well as oligonucleotideshaving non-naturally occurring portions which function similarly. Suchmodified or substituted oligonucleotides are often preferred over nativeforms because of desirable properties such as, for example, enhancedcellular uptake, enhanced affinity for a target nucleic acid andincreases stability in the presence of nucleases.

Whilst oligonucleotides are one form of the agents enabled by thepresent disclosure, other families of compounds are contemplated,including but not limited to oligonucleotide analogs and mimeticsincluding chimeras with peptides referred to as “peptideoligonucleotides”. The term “chimeras” also refers to oligonucleotidescomprising modified internucleoside linkages between naturally occurringnucleotides.

As described above, an agent in the form of an oligonucleotide generallycomprises from about 15 to about 50 nucleobases (i.e. from about 15 toabout 50-linked nucleosides).

“Targeting” an oligonucleotide agent to a particular site with α-globinmRNA in the context of the present disclosure is a multi-step processand involves in one aspect base pairing of complementary strands.

The targeting process usually includes determination of at least onetarget region, segment, or site within the α-globin mRNA which leads toreduced but not zero expression. Within the context of the presentdisclosure, the term “region” is defined as a portion of the targetnucleic acid having at least one identifiable structure, function, orcharacteristic. Within regions of target nucleic acids are segments.“Segments” are defined as smaller or sub-portions of regions within atarget nucleic acid. “Sites”, as used in the present invention, aredefined as positions within a target nucleic acid.

Alternative RNA transcripts can be produced from the same genomic regionof DNA. These alternative transcripts are generally known as “variants”.“Pre-mRNA variants” are transcripts produced from the same genomic DNAthat differ from other transcripts produced from the same genomic DNA ineither their start or stop position and contain both intronic and exonicsequence. Pre-mRNA variants of the α-globin genetic locus arecontemplated herein as a target for sense-mediated gene silencing.

Target segments can include RNA sequences that comprise at least the 15consecutive nucleobases from the 5′-terminus of the α-globin mRNAtranscript. Similarly, target segments include RNA sequences thatcomprise at least the 15 consecutive nucleobases from the 3′-terminus ofone of the α-globin mRNA transcript. The skilled artisan would, withoutundue experimentation, be able to identify further useful targetsegments. SEQ ID NO:42 through SEQ ID NO:603 and SEQ ID NO:605 to SEQ IDNO:1212 represent targets of 15 bases (15 mer's) within the α-globinmRNA. In terms of siRNA, the nucleotide sequence of a nucleotide strandof the siRNA may comprise a sequence selected from SEQ ID NO:42 throughSEQ ID NO:649. This includes hairpin RNAs. In an embodiment, thesequence or targeted sequence is selected from SEQ ID NO:25, 26, 27, 28,29, 30, 31 and 32.

Once one or more target regions, segments or sites have been identified,sense oligonucleotides are chosen which give the desired effect ofreducing translation to α-globin protein. It is not the intention of themethod to eliminate all expression of the α-globin genetic locus. It isproposed that α-globin production or gene expression be between 30% and95% the level in a normal cell (i.e. a cell from a subject who does nothave β-thalassemia).

As is known in the art, a nucleoside is a base-sugar combination. Thebase portion of the nucleoside is normally a heterocyclic base. The twomost common classes of such heterocyclic bases are the purines and thepyrimidines. Nucleotides are nucleosides that further include aphosphate group covalently linked to the sugar portion of thenucleoside. For those nucleosides that include a pentofuranosyl sugar,the phosphate group can be linked to either the 2′, 3′ or 5′ hydroxylmoiety of the sugar. In forming oligonucleotides, the phosphate groupscovalently link adjacent nucleosides to one another to form a linearpolymeric compound. In turn, the respective ends of this linearpolymeric compound can be further joined to form a circular compound,however, linear compounds are generally preferred. In addition, linearcompounds may have internal nucleobase complementarity and may,therefore, fold in a manner as to produce a fully or partiallydouble-stranded compound. Within oligonucleotides, the phosphate groupsare commonly referred to as forming the internucleoside backbone of theoligonucleotide. The normal linkage or backbone of RNA and DNA is a 3′to 5′ phosphodiester linkage.

Examples of modified oligonucleotides useful in the present methodinclude oligonucleotides containing modified backbones or non-naturalinternucleoside linkages. Oligonucleotides having modified backbonesinclude those that retain a phosphorus atom in the backbone and thosethat do not have a phosphorus atom in the backbone. Modifiedoligonucleotides that do not have a phosphorus atom in theirinternucleoside backbone can also be considered to be oligonucleosides.

Useful modified oligonucleotide backbones containing a phosphorus atomtherein include, for example, phosphorothioates, chiralphosphorothioates, phosphorodithioates, phosphotriesters,aminoalkylphosphotriesters, methyl and other alkyl phosphonatesincluding 3′-alkylene phosphonates, 5′-alkylene phosphonates and chiralphosphonates, phosphinates, phosphoramidates including 3′-aminophosphoramidate and aminoalkylphosphoramidates, thionophosphoramidates,thionoalkylphosphonates, thionoalkylphosphotriesters, selenophosphatesand boranophosphates having normal 3′-5′ linkages, 2′-5′ linked analogsof these, and those having inverted polarity wherein one or moreinternucleotide linkages is a 3′ to 3′, 5′ to 5′ or 2′ to 2′ linkage.Useful oligonucleotides having inverted polarity comprise a single 3′ to3′ linkage at the 3′-most internucleotide linkage, i.e. a singleinverted nucleoside residue which may be abasic (the nucleobase ismissing or has a hydroxyl group in place thereof). Various salts, mixedsalts and free acid forms are also included.

Useful modified oligonucleotide backbones that do not include aphosphorus atom therein have backbones that are formed by short chainalkyl or cycloalkyl internucleoside linkages, mixed heteroatom and alkylor cycloalkyl internucleoside linkages, or one or more short chainheteroatomic or heterocyclic internucleoside linkages. These includethose having morpholino linkages (formed in part from the sugar portionof a nucleoside); siloxane backbones; sulfide, sulfoxide and sulfonebackbones; formacetyl and thioformacetyl backbones; methylene formacetyland thioformacetyl backbones; riboacetyl backbones; alkene containingbackbones; sulfamate backbones; methyleneimino and methylenehydrazinobackbones; sulfonate and sulphonamide backbones; amide backbones; andothers having mixed N, O, S and CH₂ component parts.

In other useful oligonucleotide mimetics, both the sugar and theinternucleoside linkage (i.e. the backbone), of the nucleotide units arereplaced with novel groups. The nucleobase units are maintained forsequence identity with the region of α-globin transcript. One suchcompound is referred to as a peptide oligonucleotide. In peptideoligonucleotides, the sugar-backbone of an oligonucleotide is replacedwith an amide containing backbone, in particular an aminoethylglycinebackbone. The nucleobases are retained and are bound directly orindirectly to aza nitrogen atoms of the amide portion of the backbone.Teaching of peptide oligonucleotide compounds can be found in Nielsen etal. (1992) Science 254:1497-1500.

In an embodiment, oligonucleotides are provided with phosphorothioatebackbones and oligonucleosides with heteroatom backbones, and inparticular —CH₂—NH—O—CH₂—, —CH₂—N(CH₃)—O—CH₂— [known as a methylene(methlimino) or MMI backbone], —CH₂—O—N(CH₃)—CH₂—,—CH₂—N(CH₃)—N(CH₃)—CH₂— and —O—N(CH₃)—CH₂—CH₂—.

Modified oligonucleotides may also contain one or more substituted sugarmoieties. Useful oligonucleotides comprise one of the following at the2′ position: OH; F; O-, S- or N-alkyl; O-, S- or N-alkenyl; O-, S- orN-alkynyl; or O-alkyl-O-alkyl, wherein the alkyl, alkenyl and alkynylmay be substituted or unsubstituted C₁ to C₁₀ alkyl or C₂ to C₁₀ alkenyland alkynyl. Particularly preferred are O[(CH₂)_(n)O]_(m)CH₃,O(CH₂)_(n)OCH₃, O(CH₂)_(n)NH₂, O(CH₂)_(n)CH₃, O(CH₂)_(n)ONH₂, andO(CH₂)_(n)ON[(CH₂)_(n)CH₃]₂, where n and m are from 1 to about 10. Otherpreferred oligonucleotides comprise one of the following at the 2′position: C₁ to C₁₀ lower alkyl, substituted lower alkyl, alkenyl,alkynyl, alkaryl, aralkyl, O-alkaryl or O-aralkyl, SH, SCH₃, OCN, Cl,Br, CN, CF₃, OCF₃, SOCH₃, SO₂CH₃, ONO₂, NO₂, N₃, NH₂, heterocycloalkyl,heterocycloalkaryl, aminoalkylamino, polyalkylamino, substituted silyl,an RNA cleaving group, a reporter group, an intercalators, a group forimproving the pharmacokinetic properties of an oligonucleotide, or agroup for improving the pharmacodynamic properties of anoligonucleotide, and other substituents having similar properties. Onetype of modification includes 2′-methoxyethoxy (2′-O—CH₂—CH₂—OCH₃, alsoknown as 2′-O-(2-methoxyethyl) or 2′-MOE) [Martin et al. (1995) Helv.Chim. Acta, 78:486-504] i.e. an alkoxyalkoxy group. A further preferredmodification includes 2′-dimethylaminooxyethoxy, i.e. a O(CH₂)₂ON(CH₃)₂group, also known as 2′-DMAOE, as described in examples herein below,and 2′-dimethylaminoethoxyethoxy (also known in the art as2′-O-dimethyl-amino-ethoxy-ethyl or 2′-DMAEOE), i.e.2′-O—CH₂—O—CH₂—N(CH₃)₂.

Other modifications include 2′-methoxy (2′-O—CH₃), 2′-aminopropoxy(2′-OCH₂CH₂CH₂NH₂), 2′-allyl (2′-CH₂—CH═CH₂), 2′-O-allyl(2′O—CH₂—CH═CH₂) and 2′-fluoro (2′-F). The 2′-modification may be in thearabino (up) position or ribo (down) position. Similar modifications mayalso be made at other positions on the oligonucleotide, particularly the3′ position of the sugar on the 3′ terminal nucleotide or in 2′-5′linked oligonucleotides and the 5′ position of 5′ terminal nucleotide.Oligonucleotides may also have sugar mimetics such as cyclobutylmoieties in place of the pentofuranosyl sugar.

A further useful modification of the sugar includes Locked Nucleic Acids(LNAs) in which the 2′-hydroxyl group is linked to the 3′ or 4′ carbonatom of the sugar ring, thereby forming a bicyclic sugar moiety. Thelinkage is generally a methylene (—CH₂—)_(n) group bridging the 2′oxygen atom and the 4′ carbon atom wherein n is 1 or 2.

Oligonucleotides may also include nucleobase (often referred to in theart simply as “base”) modifications or substitutions. As used herein,“unmodified” or “natural” nucleobases include the purine bases adenine(A) and guanine (G), and the pyrimidine bases thymine (T), cytosine (C)and uracil (U). Modified nucleobases include other synthetic and naturalnucleobases such as 5-methylcytosine (5-me-C), 5-hydroxymethyl cytosine,xanthine, hypoxanthine, 2-aminoadenine, 6-methyl and other alkylderivatives of adenine and guanine, 2-propyl and other alkyl derivativesof adenine and guanine, 2-thiouracil, 2-thiotheymine and 2-thiocytosine,5-halouracil and cytosine, 5-propynyl (—C≡C—CH₃) uracil and cytosine andother alkynyl derivatives of pyrimidine bases, 6-azo uracil, cytosineand thymine, 5-uracil (pseudouracil), 4-thiouracil, 8-halo, 8-amino,8-thiol, 8-thioalkyl, 8-hydroxyl and other 8-substituted adenines andguanines, 5-halo particularly 5-bromo, 5-trifluoromethyl and other5-substituted uracils and cytosines, 7-methylguanine and7-methyladenine, 2-F-adenine, 2-amino-adenine, 8-azaguanine and8-azaadenine, 7-deazaguanine and 7-deazaadenine and 3-deazaguanine and3-deazaadenine. Further modified nucleobases include tricyclicpryimidines such as phenoxazine cytidine (1H-pyrimido[5,4-b][1,4]benzoxazin-2(3H)-one), phenothiazine cytidine (1H-pyrimido[5,4-b][1,4]benzothiazin-2(3H)-one), G-clamps such as a substituted phenoxazinecytidine (e.g. 9-(2-aminoethoxy)-H-pyrimido[5,4-b][1,4]benzoxazin-2(3H)-one), carbazole cytidine(2H-pyrimido[4,5-b]indol-2-one), pyridoindole cytidine (H-pyrido[3′,2′:4,5]pyrrole[2,3-d]pyrimidin-2-one). Modified nucleobases may alsoinclude those in which the purine or pyrimidine base is replaced withother heterocycles, for example 7-deaza-adenine, 7-deazaguanosine,2-aminopyridine and 2-pyridone. Certain of these nucleobases areparticularly useful for increasing the binding affinity of the agents ofthe present invention. These include 5-substituted pyrimidines,6-azapyrimidines and N-2, N-6 and O-6 substituted purines, including2-aminoprophyladenine, 5-prophynyluracil and 5-propynylcytosine.5-methylcytosine substitutions have been shown to increase nucleic acidduplex stability.

Another modification of the oligonucleotides enabled herein involveschemically linking to the oligonucleotide one or more moieties orconjugates which enhance the activity, cellular distribution or cellularuptake of the oligonucleotide. These moieties or conjugates can includeconjugate groups covalently bound to functional groups such as primaryor secondary hydroxyl groups. Conjugate groups of the invention includeintercalators, reporter molecules, polyamines, polyamides, polyethyleneglycols, polyethers, groups that enhance the pharmacodynamic propertiesof oligomers, and groups that enhance the pharmacokinetic properties ofoligomers. Typical conjugate groups include cholesterols, lipids,phospholipids, biotin, phenazine, folate, phenanthridine, anthraquinone,acridine, fluoresceins, rhodamines, coumarins and dyes. Groups thatenhance the pharmacodynamic properties, in the context of thisinvention, include groups that improve uptake, enhance resistance todegradation, and/or strengthen sequence-specific hybridization with thetarget nucleic acid. Groups that enhance the pharmacokinetic properties,in the context of the present invention, include groups that improveuptake, distribution, metabolism or excretion of the compounds of thepresent invention. Conjugate moieties include but are not limited tolipid moieties such as a cholesterol moiety, cholic acid, a thioether,e.g. hexyl-S-tritylthiol, a thiocholesterol, an aliphatic chain, e.g.dodecandiol or undecyl residues, a phospholipid, e.g.di-hexadecyl-rac-glycerol or triethyl-ammonium1,2-di-O-hexadecyl-rac-glycero-3-H-phosphonate, a polyamine or apolyethylene glycol chain, or adamantine acetic acid, a palmitoylmoiety, or an octadecylamine or hexylamino-carbonyl-oxycholeterolmoiety. Oligonucleosides of the invention may also be conjugated toactive drug substances, for example, aspirin, warfarin, phenylbutazone,ibuprofen, suprofen, fenbufen, ketoprofen, (S)-(+)-pranoprofen,carprofen, dansylsarcosine, 2,3,5-triiodobenzoic acid, flufenamic acid,folinic acid, a benzothiadiazide, chlorothiazide, a diazepine,indomethicin, a barbiturate, a cephalosporin, a sulfa drug, anantidiabetic, an antibacterial or an antibiotic.

It is not necessary for all positions in a given compound to beuniformly modified, and in fact more than one of the aforementionedmodifications may be incorporated in a single compound or even at asingle nucleoside within an oligonucleotide.

Taught herein is sense oligonucleotides which are chimeric compounds.“Chimeric” sense oligonucleotides or “chimeras”, in the context of thepresent method, are oligonucleotides which contain two or morechemically distinct regions, each made up of at lest one monomer unit,i.e. a nucleotide in the case of an oligonucleotide compound. Theseoligonucleotides typically contain at least one region wherein theoligonucleotide is modified so as to confer upon the oligonucleotideincreased resistance to nuclease degradation, increased cellular uptake,increased stability and/or increased binding affinity of the targetnucleic acid.

Chimeric oligonucleotides may be formed as composite structures of twoor more oligonucleotides, modified oligonucleotides, oligonucleosidesand/or oligonucleotide mimetics as described above.

A gene therapy approach may also be used to obtain DNA-derived orRNA-derived siRNA or other RNA species including hairpin RNAs.

A nucleic acid sequence encoding an RNA species such as siRNA may beintroduced into a cell in a vector such that the nucleic acid sequenceremains extrachromosomal. In such a situation, the nucleic acid sequencewill be expressed by the cell from the extrachromosomal location.Alternatively, cells may be engineered by inserting the nucleic acidsequence into the chromosome. Vectors for introduction of nucleic acidsequence both for recombination and for extrachromosomal maintenance areknown in the art and any suitable vector may be used. Methods forintroducing nucleic acids into cells such as electroporation, calciumphosphate co-precipitation and viral transduction are known in the art.

In particular, a number of viruses have been used as nucleic acidtransfer vectors or as the basis for preparing nucleic acid transfervectors, including papovaviruses (e.g. SV40, Madzak et al. (1992) J GenVirol 73:1533-1536), adenovirus (Berkner (1992) Curr Top MicrobiolImmunol 158:39-66; Berkner et al. (1988) BioTechniques 6:616-629;Gorziglia and Kapikian (1992) J Virol 66:4407-4412; Quantin et al.(1992) Proc Natl Acad Sci USA 89:2581-2584; Rosenfeld et al. (1992) Cell68:143-155; Wilkinson et al. (1992) Nucleic Acids Res 20:233-2239;Stratford-Perricaudet et al. (1990) Hum Gene Ther 1:241-256; Schneideret al. (1998) Nat Genetics 18:180-183), vaccinia virus (Moss (1992) CurrTop Microbiol Immunol 158:5-38; Moss (1996) Proc Natl Acad Sci USA93:11341-11348), adeno-associated virus (Muzyczka (1992) Curr TopMicrobiol Immunol 158:97-129; Ohi et al. (1990) Gene 89:279-282; Russelland Hirata (1998) Nat Genetics 18:323-328), herpesviruses including HSVand EBV (Margolskee (1992) Curr Top Microbiol Immunol 158:67-95; Johnsonet al. (1992) J Virol 66:2952-2965; Fink et al. (1992) Hum Gene Ther3:1-19; Breakefield and Geller (1987) Mol Neurobiol 1:339-371; Freese etal. (1990) Biochem Pharmaco. 40:2189-2199; Fink et al. (1996) Ann RevNeurosci 19:265-287), lentiviruses (Naldini et al (1996) Science272:263-267), Sindbis and Semliki Forest virus (Berglund et al. (1993)Biotechnology 11:916-920) and retroviruses of avian (Bandyopadhyay andTemin (1984) Mol Cell Biol 4:749-754; Petropoulos et al. (1992) J Virol66:3391-3397), murine (Miller (1992) Curr Top Microbiol Immunol158:1-24; Miller et al. (1985) Mol Cell Biol 5:431-437; Sorge et al.(1984) Mol Cell Biol 4:1730-1737; Mann and Baltimore (1985) J Virol54:401-407; Miller et al. (1988) J Virol 62:4337-4345) and human(Shimada et al. (1991) J Clin Invest 88:1043-1047; Helseth et al. (1990)J Virol 64:2416-2420; Page et al. (1990) J Virol 64:5270-5276;Buchschacher and Panganiban (1982) J Virol 66:2731-2739) origin.Lentiviral vectors represent a particularly useful vector for genetherapy. In one embodiment, the lentivirus vector comprises amono-cistronic vector for tissue-specific expression of an siRNA orother RNA species using a erythroid-derived polymerase (pol) IIpromoter.

In an embodiment, the vector contains the human β-globin gene under thecontrol of the pol II β-globin promoter. Hairpin RNAs targeting sites onthe α-globin gene or transcript can be inserted in introns or in the 3′-or 5′-UTR of the β-globin gene.

Taught herein is a vector comprising a nucleic acid molecule encodinghuman β-globin operably linked to a promoter and one or more nucleicacid molecules inserted in the 5′- and/or 3′-UTR region and/or intronicregions of the β-globin nucleic acid molecule encoding an RNA whichtargets an mRNA species encoding α-globin at a site selected from the 5′untranslated region (5′-UTR), Exon1, Exon3 and the 3′-UTR or a boundaryregion inbetween.

In an embodiment, the promoter is the pol II or pol III promoter.

In an embodiment, the second nucleic acid molecule encodes an RNA whichtargets or comprises α-globin mRNA selected from SEQ ID NO:25, 26, 27,28, 29, 30, 31 and 32.

In an embodiment, the RNA molecules targeting the α-globin mRNA speciesare encoded by sequences inserted into β-globin nucleic acid molecule soas to facilitate combination therapy of providing β-globin and reducingα-globin.

Non-viral nucleic acid transfer methods are known in the art such aschemical techniques including calcium phosphate co-precipitation,mechanical techniques, for example, microinjection, membranefusion-mediated transfer via liposomes and direct DNA uptake andreceptor-mediated DNA transfer. Viral-mediated nucleic acid transfer canbe combined with direct in vivo nucleic acid transfer using liposomedelivery, allowing one to direct the viral vectors to particular cells.Alternatively, the retroviral vector producer cell line can be injectedinto particular tissue. Injection of producer cells would then provide acontinuous source of vector particles.

The agent herein may also be admixed, encapsulated, conjugated orotherwise associated with other molecules, molecule structures ormixtures of compounds, as for example, liposomes, receptor-targetedmolecules, oral, rectal, topical or other formulations, for assisting inuptake, distribution and/or absorption.

The agents contemplated for use herein encompass any pharmaceuticallyacceptable salts, esters, or salts or such esters, or any other compoundwhich, upon administration to a human, is capable of providing (directlyor indirectly) the biologically active metabolite or residue thereof.Accordingly, for example, the disclosure if also drawn to prodrugs andpharmaceutically acceptable salts of the compounds of the invention,pharmaceutically acceptable salts of such prodrugs and otherbioequivalents.

The term “prodrug” indicates a therapeutic agent that is prepared in aninactive form that is converted to an active form (i.e. drug) within thebody or cells thereof by the action of endogenous enzymes or otherchemicals and/or conditions. In an example, prodrug versions of theoligonucleotides described herein are prepared as SATE[(S-acetyl-2-thioethyl)phosphate] derivatives.

The term “pharmaceutically acceptable salts” refers to physiologicallyand pharmaceutically acceptable salts of the compounds, i.e. salts thatretain the desired biological activity of the parent compound and do notimpart undesired toxicological effects thereof.

Also taught herein are pharmaceutical compositions and formulationswhich include the agents herein described. The pharmaceuticalcompositions may be administered in any number of ways depending uponwhether local or systemic treatment is desired and upon the area to betreated. Administration may be topical (including ophthalmic and tomucous membranes including vaginal and rectal delivery), pulmonary, e.g.by inhalation or insufflation of powders or aerosols, including bynebulizer; intratracheal, intranasal, epidermal and transdermal, oral orparenteral. Parenteral administration includes intravenous,intraarterial, subcutaneous, intraperitoneal or intramuscular injectionor infusion; or intracranial, e.g. intrathecal or intraventricular,administration. Oligonucleotides with at least one 2-O-methoxyethylmodification are believed to be particularly useful for oraladministration. Pharmaceutical compositions and formulations for topicaladministration may include transdermal patches, ointments, lotions,creams, gels, drops, suppositories, sprays, liquids and powders.Conventional pharmaceutical carriers, aqueous, powder or oily bases,thickeners and the like may be necessary or desirable. Coated condoms,gloves and the like may also be useful.

The pharmaceutical formulations herein, which may conveniently bepresented in unit dosage form, may be prepared according to conventionaltechniques well known in the pharmaceutical industry. Such techniquesinclude the step of brining into association the active ingredients withthe pharmaceutical carrier(s) or excipient(s). In general, theformulations are prepared by uniformly and intimately bringing intoassociation the active ingredients with liquid carriers or finelydivided solid carriers or both, and then, if necessary, shaping theproduct.

The compositions herein may be formulated into any of many possibledosage forms such as, but not limited to, tablets, capsules, gelcapsules, liquid syrups, soft gels, suppositories and enemas. Thecompositions herein may also be formulated a suspensions in aqueous,non-aqueous or mixed media. Aqueous suspensions may further containsubstances which increase the viscosity of the suspension including, forexample, sodium carboxymethylcellulose, sorbitol and/or dextran. Thesuspension may also contain stabilizers.

Pharmaceutical compositions include, but are not limited to, solutions,emulsions, foams and liposome-containing formulations. Thepharmaceutical compositions and formulations may comprise one or morepenetration enhancers, carriers, excipients or other active or inactiveingredients.

Formulations enabled herein include liposomal formulations. The term“liposome” means a vesicle composed of amphililic lipids arranged in aspherical bilayer or bilayers. Liposomes are unilamellar ormultilamellar vesicles which have a membrane formed from a lipophilicmaterial and an aqueous interior that contains the composition to bedelivered. Cationic liposomes are positively charged liposomes which arebelieved to interact with negatively charged RNA molecules to form astable complex. Liposomes that are pH-sensitive or negatively-chargedare believed to entrap DNA rather than complex with it. Both cationicand noncationic liposomes have been used to deliver RNA to cells.

Liposomes also include “sterically stabilized” liposomes, a term which,as used herein, refers to liposomes comprising one or more specializedlipids that, when incorporated into liposomes, result in enhancedcirculation lifetimes relative to liposomes lacking such specializedlipids. Examples of sterically stabilized liposomes are those in whichpart of the vesicle-forming lipid portion of the liposome comprises oneor more glycolipids or is derivatized withy one or more hydrophilicpolymers, such as a polyethylene glycol (PEG) moiety.

In one embodiment, various penetration enhancers are employed to effectthe efficient delivery of nucleic acids, such as oligonucleotides. Inaddition to aiding the diffusion of non-lipophilic drugs across cellmembranes, penetration enhancers also enhance the permeability oflipophilic drugs. Penetration enhancers may be classified as belongingto one of five broad categories, i.e. surfactants, fatty acids, bilesalts, chelating agents and non-chelating non-surfactants.

The skilled artisan will recognize that formulations are routinelydesigned according to their intended uses, i.e. route of administration.

Useful formulations for topical administration include those in whichthe oligonucleotides are in admixture with a topical delivery agent suchas lipids, liposomes, fatty acids, fatty acid esters, steroids,chelating agents and surfactants. Lipids and liposomes include neutral(e.g. dioleoylphosphatidyl DOPE ethanolamine, dimyristoylphophatidylcholine DMPC, distearolyphosphatidyl choline) negative (e.g.dimyristoylphosphatidyl glycerol DMPG) and cationic (e.g.dioleoyltetramethylaminopropyl DOTAP and dioleoylphosphatidylethanolamine DOTMA).

For topical or other administration, the oligonucleotides may beencapsulated within liposomes or may form complexes thereto, inparticular to cationic liposomes. Alternatively, oligonucleotides may becomplexed to lipids, in particular to cationic lipids.

Compositions and formulations for oral administration include powders orgranules, microparticulates, nanoparticulates, suspensions or solutionsin water or non-aqueous media, capsules, gel capsules, sachets, tabletsor minitablets. Thickeners, flavoring agents, diluents, emulsifiers,dispersing aids or binders may be desirable. Oral formulations includethose in which oligonucleotides are administered in conjunction with oneor more penetration enhancers surfactants and chelators. Usefulsurfactants include fatty acids and/or esters or salts thereof, bileacids and/or salts thereof.

The term “subject” as used herein includes a human subject. The humansubject may be male or female and any age from infant to elderly. Foranimal model studies, the subject may be a non-human animal including alaboratory test animal, farm animal or primate.

Compositions and formulations for parenteral, intrathecal orintraventricular administration may include sterile aqueous solutionswhich may also contain buffers, diluents and other suitable additivessuch as, but not limited to, penetration enhancers, carrier compoundsand other pharmaceutically acceptable carriers or excipients. Thecompositions may also be cell based or viral compositions.

The formulation of therapeutic compositions and their subsequentadministration (dosing) is within the skill of those in the art. Dosingis dependent on severity and responsiveness of the β-thalassemic diseasestate, with the course of treatment lasting from several days to severalmonths or years, or until a cure is effected or a diminution of thedisease state is achieved. Optimal dosing schedules can be calculatedfrom measurements of drug accumulation in the body of the patient.Persons of ordinary skill can easily determine optimum dosages, dosingmethodologies and repetition rates. Optimum dosages may vary dependingon the relative potency of individual oligonucleotides, and cangenerally be estimated based on EC₅₀s found to be effective in in vitroand in vivo animal models. In general, dosage is from 0.01 μg to 100 gper kg of body weight, and may be given once or more daily, weekly,monthly or yearly, or even every 2 to 20 years. Persons of ordinaryskill in the art can easily estimate repetition rates for dosing basedon measured residence times and concentrations of the drug in bodilyfluids or tissues. Following successful treatment, it may be desirableto have the patient undergo maintenance therapy to prevent therecurrence of the disease state, wherein the oligonucleotide isadministered in maintenance doses, ranging from 0.01 μg to 100 g per kgof body weight, once or more daily, to once every 20 years.

The present disclosure is instructional on the use of an agent whichreduces expression of the α-globin genetic locus in a subject in themanufacture of a medicament in the treatment of β-thalassemia or arelated hemoglobinopathy.

A related embodiment teaches an agent which reduces expression of theα-globin genetic locus in a method for treating β-thalassemia or arelated hemoglobinopathy.

Further enabled herein is a method for treating β-thalassemia or arelated hemoglobinopathy in a human subject, the method comprisingadministering to the subject an siRNA molecule of from 15 to 50 bp inlength which targets a region on α-globin mRNA selected from the listconsisting of 5′-UTR, 3′-UTR, Exon1, Exon3 and a boundary or intronicregion to thereby reduce the level of expression of the α-globin geneticlocus to less than levels prior to intervention to above-zero levels,the amount of siRNA administered being effective to reduce α-globinlevels to re-balance the levels of α-globin and β-globin. Targetsinclude SEQ ID NO:42 to SEQ ID NO:603 on HBA1 and SEQ ID NO:605 to SEQID NO:1212 on HBA2 with the exception of Hs-siα5, CNα2 and CNα3.

Examples of siRNA include SEQ ID NO:25, 26, 27, 28, 29, 30, 31 and 32 aswell as hairpin forming thereof. Another aspect enabled herein isdirected to a vector comprising a nucleic acid molecule encoding humanβ-globin operably linked to a promoter and one or more second nucleicacid molecules inserted in the 5′-UTR and/or 3′-UTR region and/or anintron of the β-globin-encoding nucleic acid molecule which secondnucleic acid molecule encodes an RNA which targets an mRNA speciesencoding α-globin at a site selected from the 5′ untranslated region(5′-UTR), Exon1, Exon3 and the 3′-UTR or a boundary region inbetween. Inan embodiment, the vector provides therapeutic levels of β-globin whilereducing α-globin levels.

In an embodiment, the siRNA comprises a nucleotide sequence selectedfrom SEQ ID NO:42 through SEQ ID NO:603 on HBA1 or SEQ ID NO:605 to SEQID NO:1212 on HBA2 or targets a nucleotide sequence selected from SEQ IDNO:42 through SEQ ID NO:603 or SEQ ID NO:605 to SEQ ID NO:1212.

EXAMPLES

Aspects disclosed herein are now further described by the followingnon-limiting Examples.

Materials and Methods Maintenance of Cell Lines

In these studies, human erythroleukaemic K562 cells were maintained incontinuous culture in Dulbecco's Modified Eagle Media (DMEM) (Sigma,Sydney, NSW, Australia) supplemented with 10% v/v fetal calf serum(FCS), 100 U/ml penicillin and 100 μg/ml streptomycin. Cells wereincubated at 37° C. and passaged every 3-4 days by adding 2 ml of aconfluent culture to 20 ml growth medium in an 80 cm² flask. Cells wereseeded at 1×10⁵ cells/ml 12 hours prior to transfection.

MEL cells were induced to hemoglobinize by seeding at an initialconcentration of 2×10⁵ cells per ml in DMEM containing 2% w/v DMSO(Sigma) and incubated at 37° C. After five days of hemoglobinization,cells were resuspended at 5×10⁵ cells per ml in fresh DMEM with 2% w/vDMSO (Scher et al. (1982) Cancer Res. 42:1300-1306) and electroporatedapproximately 16 hours later.

Electroporation of Mammalian Cells

Immediately preceding electroporation, cells were washed three timeswith equal volumes of Opti-Mem reduced serum media (Invitrogen) andresuspended at a final concentration of 1×10⁷ K562 cells per ml inOpti-Mem. Electroporations were performed at room temperature in 0.4 cmcuvettes (Bio-Rad, Hercules, Calif.) with 500 μl cell suspension mixedwith an appropriate amount of RNA or DNA resuspended at a concentrationof 1 μg/μl. Electroporations were performed on the Gene Pulser (Bio-Rad)using the following conditions: 226 Volts, 950 μF and ∞ resistance forK562 cells or 250 Volts. Cells were then cultured in 10 ml DMEMcontaining 10% v/v FCS.

Flow Cytometry

At various time points following transfection, cells were analysed withan LSR II flow cytometer (Becton Dickson, Franklin Lakes, Calif., USA).Briefly, 0.1-1×10⁶ cells were washed once in PBS supplemented with 1%v/v FBS and resuspended in a final volume of 0.5 ml PBS. For thedetection of eGFP reporter gene expression, analysis was performed onlyon live cells. Data acquisition and analysis were performed using BDFACsDiva software (Becton Dickson).

RNA Extractions

Cells were collected at appropriate time points after transfections andRNA was extracted using Tri-Reagent (Molecular Research Centre,Cincinnati, Ohio) according to manufacturer's instructions. Briefly,between 2.5-5×10⁶ cells were collected by centrifugation and lysed in500 μl Tri-Reagent for 5 minutes. 100 μl of chloroform was added andsamples were agitated thoroughly for 30 seconds. Phase separation wasachieved by centrifugation at 13,000 g for 20 minutes at 4° C. Theaqueous phase was collected and RNA was precipitated by incubation withequal volume isopropanol. RNA was collected by centrifugation at 13,000g for 10 minutes at 4° C., washed with 1 ml 75% v/v ethanol andresuspended in 50 μl nuclease-free H₂O. Quantity and quality of RNA wasdetermined by spectrophotometry.

cDNA Synthesis

cDNA was synthesized using SuperScript First-Strand kit (Invitrogen)according to manufacturer's instructions. In brief, 1 μg of RNA wascombined with 1 μl of 0.5 μg/μl oligo (dT) primers, 1 μl 10 mM dNTPs andnuclease-free H₂O to a final volume of 10 μl l and incubated at 65° C.for 5 minutes. Reactions were placed on ice prior to the addition of 2μl reaction buffer (200 mM Tris-HCl (pH 8.4), 500 mM KCl), 4 μl 25 mMMgCl₂, 2 μl 0.1 mM DTT and 1 μl RNAseOut and incubated at 42° C. for 2minutes. Reverse transcription then proceeded with the addition of 1 μlSuperscript II (50 units/μl) enzyme at 42° C. for 50 minutes followed bytermination at 70° C. for 15 minutes.

Real-Time PCR

All samples were analyzed using primer sets designed using PrimerExpress software (Applied Biosystems, Epsom, Surrey). Reactions wereperformed on a 7300 Real-Time PCR System (Applied Biosystems). 25 ng oftemplate cDNA was combined with 2 pmol of the forward primer and 2 pmolof the reverse primer and 12.5 μl SYBR Green Master Mix (AppliedBiosystems) to a final volume of 25 μl. Samples were held at 50° C. for2 minutes then 95° C. for 10 minutes followed by 40 cycles of 15 secondsat 95° C. and 1 minute at 60° C. with data collection occurring at 60°C. A final dissociation stage was performed consisting of 15 seconds at95° C., 30 seconds at 60° C. and 15 seconds at 95° C. All reactions wereperformed in triplicates.

Data Analysis

Triplicate cycle threshold (Ct) values for each sample and primer pairwere averaged. The Ct value is the number of cycles required for a labelsignal to cross the threshold (i.e. exceeds background level). The Ctlevel is inversely proportional to the amount of target to nucleic acidin a sample. Ct value of the gene of interest (α-globin) was subtractedfrom the reference gene (β-actin or β-globin) to calculate Δ Ct. Theformula 2^(ΔCt) was applied to give fold-difference between α-globinrelative to the reference gene. Reductions of α-globin expression weredetermined by dividing fold-differences in experimental group againstfold-differences in mock electroporated MEL cells.

Example 1 Phenotypic Improvements in β-thalassemic Cells

One of the mechanisms by which excess α-globin chains are believed todamage erythroid progenitor cells is through the increased generation ofROS (Advani et al. (1992) supra; Schrier and Mohandas (1992) Blood79:15896-1592; Schrier et al. (1989) Blood 74:2194-2202; Scott et al.(1993) J Clin Invest 91:1706-1712). Each improperly paired α-chain alsocarries an attached heme group and iron molecule which can be oxidizedin the highly oxygenated environment of a RBC (Schrier (2002) supra).The increased ROS arising from imbalanced globin synthesis was detectedby incubating cultured mouse β-KO cells with 2,7-dichlorofluoresceindiacetate (DCFH) [Amer et al. (2003) Eur J Haematol 70:84-90; Kong etal. (2004) J Clin Invest 114:1457-1466, and Wannasuphaphol et al. (2005)Ann N Y Acad Sci 1054:407-416] (FIG. 1B(i)). Levels of ROS in culturederythroid progenitor cells from β-KO and WT mice were similar to levelsdetected in the peripheral RBCs from these mice, with β-KO cellsgenerating ROS at levels double that of WT mice (FIG. 1B(i)). However,when β-KO cells were treated with siα4, the reduction in α-globinexpression resulted in decreased levels of ROS and partial normalizationof thalassemic phenotype as measured by DCFH fluorescence. Cells treatedwith 10 μg and 5 μg of siα4, which showed the greatest decrease inα-globin mRNA, also showed the greatest improvements in ROS levels withreductions of 41%±13% (P<0.05) and 26%±4% (P<0.02), respectively. Incontrast, levels of DCFH fluorescence in cells treated with 1 μg and 10μg siLuc were not significantly different from mock electroporated cells(FIG. 1B(ii)).

Most importantly, the results illustrate that reduced α-globinexpression resulted in a detectable phenotypic change in thalassemicerythroid cells, decreasing ROS production to WT levels. This providesclear evidence that the heterozygous β-KO mouse is a suitable in vivomodel for testing therapeutic down-regulation of α-globin. In summation,the results provide the basis for an innovative new strategy to treatβ-thalassemia.

Example 2 siRNA-Mediated Reductions of Murine α-Globin

In developing a strategy to treat β-thalassemia patients, thesusceptibility of human α-globin to siRNA-mediated degradation istested.

Although α-globin is highly conserved between mouse and humans, it isdifficult to isolate regions of perfect homology suitable for effectivesiRNA targeting in the relatively short (˜500 bp) mRNA sequences.Effective siRNA design generally requires a low GC content with a GCbias towards the 5′ end to maintain appropriate thermodynamic stability(Patzel (2007) Drug Discov Today 12:139-148). However, the α-globin geneis notoriously GC-rich (Higgs et al. (1989) Blood 73:1081-1104), makingsiRNA selection somewhat challenging. In addition, many siRNA selectionguidelines recommend specific nucleotides in particular positions(Patzel (2007) supra), further limiting the available targets. Hence,siRNAs demonstrated to be effective against murine α-globin may notnecessarily remain so against human sequences. Therefore, in order tomaximize efficacy, siRNAs specific to human α-globin are designed andscreened in an appropriate system.

The K562 cells are one of the most well characterized human erythroidcell lines. Originally derived from a patient with chronic myelogenousleukaemia (Lozzio and Lozzio (1975) Blood 45:321-334), these cells growcontinuously in culture and display erythroid characteristics such asthe expression of glycophorin A, the major sialoglycoprotein on humanred cells (Anderson et al. (1979) Int J Cancer 23:143-147). In addition,K562 cells express low levels of hemoglobin, consistent with an earlyerythroid progenitor phenotype (Miller et al. (1984) Blood 63:195-200).The expressed globin chains are predominantly embryonic in nature, withε β-like chains and ζ α-like chains, but some fetal hemoglobin (γ₂α₂) isalso produced (Rutherford et al. (1981) Proc Natl Acad Sci USA78:348-352). α-Globin, therefore, is expressed at low but detectablelevels, sufficient for preliminary screening experiments and previousstudies using antisense (Ponnazhagan et al. (1994) J Exp Med179:733-738) or ribozyme (Shen et al. (1999) Blood Cells Mol ids25:361-373) strategies to reduce α-globin have also utilized K562 cellsas the model system.

In this example, low doses of siRNA were electroporated into K562 cellsand reductions were detected by real-time PCR at 24 and 48 hours. ThesiRNA's used are shown in Table 3. A total of eight siRNAs targetinghuman α-globin were tested in this manner and a number of these werefound to be effective, generating reductions in α-globin comparable topreviously tested strategies. These results identify siRNA sequenceswhich are able to retain a high level of efficacy in primary erythroidprogenitor cells.

TABLE 3 siRNA sequences SEQ ID Name Sequence (5′ to 3′) NO:Marine siRNA sequences si-α1 sense r(GGAGCUGAAGCCCUGGAAA)dTdT  1si-α1 antisense r(UUUCCAGGGCUUCAGCUCC)dAdT  2 si-α2 senser(AGGUCAAGGGUCACGGCAA)dTdT  3 si-α2 antisense r(UUGCCGUGACCCUUGACCU)dGdG 4 si-α3 sense r(CCGUGCUGACCUCCAAGUA)dTdT  5 si-α3 antisenser(UACUUGGAGGUCAGCACGG)dTdG  6 si-α4 sense r(CCUCUUGGUCUUUGAAUAA)dTdT  7si-α4 antisense r(UUAUUCAAAGACCAAGAGG)dTdA  8Murine ShRNA oligonucleotides pshα1 oligoGAT CCC CAT GGA GCT GAA GCC CTG GAA  9 FWD ATT CAA GAGATT TCC AGG GCT TCA GCT CCA TTT TTT 10 A pshα1 oligoAGC TTA AAA AAT GGA GCT GAA GCC CTG 11 REV GAA ATC TCTTGA ATT TCC AGG GCT TCA GCT CCA TGG 12 G pshα2 oligoGAT CCC CCC AGG TCA AGG GTC ACG GCA 13 FWD ATT CAA GAGATT GCC GTG ACC CTT GAC CTG GTT TTT 14 A pshα2 oligoAGC TTA AAA ACC AGG TCA AGG GTC ACG 15 REV GCA ATC TCTTGA ATT GCC GTG ACC CTT GAC CTG GGG 16 G pshα3 oligoGAT CCC CC CCG TGC TGA CCT CCA AGT 17 FWD ATT CAA GAGATA CTT GGA GGT CAG CAC GGT GTT TTT 18 A pshα3 oligoAGC TTA AAA ACA CCG TGC TGA CCT CCA 19 REV AGT ATC TCTTGA ATA CTT GGA GGT CAG CAC GGT GGG 20 G pshα4 oligoGAT CCC CTA CCT CTT GGT CTT TGA ATA 21 FWD ATT CAA GAGATT ATT CAA AGA CCA AGA GGT ATT TTT 22 A pshα4 oligoAGC TTA AAA ATA CCT CTT GGT CTT TGA 23 REV ATA ATC TCTTGA ATT ATT CAA AGA CCA AGA GGT AGG 24 G Human siRNA sequencesHs_si-α1 sense r(CAGACUCAGAGAGAACCCA)dTdT 25 Hs_si-α1r(UGGGUUCUCUCUGAGUCUG)dTdG 26 antisense Hs_si-α2 senser(CCGACAAGACCAACGUCAA)dTdT 27 Hs_si-α2 r(UUGACGUUGGUCUUGUCGG)dCdA 28antisense Hs_si-α3 sense r(CCGUGCUGACCUCCAAAUA)dTdT 29 Hs_si-α3r(UAUUUGGAGGUCAGCACGG)dTdG 30 antisense Hs_si-α4 senser(GGCCCUUCCUGGUCUUUGA)dTdT 31 Hs_si-α4 r(UCAAAGACCAGGAAGGGCC)dGdG 32antisense Hs_si-α5 sense r(GACCUACUUCCCGCACUUC)dTdT 33 Hs_si-α5r(GAAGUGCGGGAAGUAGGUC)dTdT 34 antisense Stealth si-α1GCCCUGGAGAGGAUGUUCCUGUCCU 35 sense Stealth si-α1AGGACAGGAACAUCCUCUCCAGGGC 36 antisense Stealth si-α2CCACCAAGACCUACUUCCCGCACUU 37 sense Stealth si-α2AAGUGCGGGAAGUAGGUCUUGGUGG 38 antisense Stealth si-α3CCGUGCUGACCUCCAAAUACCGUUA 39 sense Stealth si-α3UAACGGUAUUUGGAGGUCAGCACGG 40 antisense

Example 3 Human siRNA Sequences

For identifying effective siRNAs targeting human α-globin (see Table 3),a total of eight siRNA sequences were tested in K562 cells. Qiagendesign algorithms were utilized to identify four sequences targeting themajor α2-globin gene. Two of four siRNAs selected in this fashion werehomologous to murine si-α3 and si-α4, sequences previously demonstratedto be effective in MEL cells (see FIGS. 2A and B). However, the si-α4human homolog binds a region in the 3′ UTR which differs between thehuman α1 and α2 globin genes. The equivalent region in the α1-globingene was considered unsuitable for siRNA targeting as it failed to meetmany of the recommended guidelines so the Hs-siα4 sequence only targetsthe α2-globin sequence. In addition to these pre-designed sequences, afifth siRNA was designed against the 5′ region of Exon 2. A study(Sarakul et al. (2008) supra) has reported that siRNAs targeting thisregion reduced α-globin expression substantially in cultured normalerythroid precursor cells so the Hs-siα5 sequence was included forcomparison.

It was also of interest to investigate the effects of varying siRNAcomposition on silencing ability so, in addition to the five siRNAssynthesized with standard chemistries, three additional Stealth (TradeMark) siRNAs from Invitrogen were also tested. The Stealth (Trade Mark)siRNAs are blunt-ended 25 bp dsRNA molecules chemically modified toenhance stability and minimize off target effects. As these moleculesdiffer slightly from standard siRNAs, parameters for predicting optimalsequences also varies slightly. Nevertheless, two of the three topStealth (Trade Mark) sequences recommended by Invitrogen's algorithmsmatched target sites selected for standard siRNAs (FIGS. 2A and B). TheStealth St-siα3 matched a Qiagen sequence (si-α3) while St-siα2overlapped with the previously published si-α5 sequence.

Example 4 siRNA-Mediated Reductions of α-Globin in Human ErythroleukemicCells

α-Globin mRNA in K562s Treated with 1 μg siRNA

As the levels of α-globin expression in K562 cells are relatively low, asmall quantity of siRNA was initially utilized in order to identify themost effective sequences. 1 μg of siRNA was electroporated into 5×10⁶K562 cells and α-globin mRNA expression was determined at 24 and 48hours by real-time PCR with β-actin as a loading control.

Three of the siRNA sequences tested (Hs-siα3, Hs-siα4 and Hs-siα5) hadno significant effects on α-globin expression at 24 hours.Interestingly, the St-siα2 and St-siα3 Stealth sequences, which overlapwith Hs-siα5 and Hs-siα3, respectively, generated significant reductionsin α-globin expression compared to mock electroporated K562s. BothSt-siα1 and St-siα3 reduced α-globin expression by ˜50% (P<0.05) whileSt-siα2 generated a greater reduction of ˜78%±3% (P<0.0005) at the mRNAlevel. However, the greatest knockdowns were observed in cells treatedwith 1 μg of Hs-siα1 and Hs-siα2. 1 μg of Hs-siα1 reduced α-globinexpression by 90%±4% (P<0.001) while Hs-siα2 generated reductions of85%±6% (P<0.005) [FIG. 3].

At 48 hours, cells treated with the Stealth sequences appeared torecover α-globin expression while standard siRNAs either retained orincreased reductions. Cells treated with St-siα1 recovered fastest andwere no longer significant at 48 hours. St-siα2 was also less active at48 hours with only 57%±8% (P<0.01) reduction while St-siα3 retained thesame degree of efficacy with reductions of 50%±14% (P<0.05). Hs-siα1 andHs-siα2 both retained efficacies at 48 hours with reductions of 97%±3%(P<0.0005) and 82% (P<0.0001) respectively. Hs-siα4, which only targetsα2-globin, was much more effective at 48 hours compared to 24 hours,reducing α-globin by 47%±9% (P<0.05) compared to mock electroporatedcells (FIG. 3).

Example 5 α-Globin mRNA in K562s Treated with 500 ng siRNA

In order to better assess the efficacy of each siRNA sequence, smalleramounts of siRNA were delivered into K562s and effects on α-globinexpression was again determined by real-time PCR. At 24 hours, thislower dose of siRNA was able to clearly indicate the most effectivetargets. While all siRNAs except Hs-siα3 and Hs-siα5 generatedsignificant reductions in α-globin, three of these were relativelymodest. An amount of 500 ng of Hs-siα4, St-siα1 and St-siα3 reducedα-globin expression by 25%±5%, 19%±7% and 29%±10% respectively, comparedto Mock electroporated controls (P<0.05) [FIG. 4]. The Hs-siα1, Hs-siα2and St-siα2 sequences previously demonstrated to be most effective weremarkedly more so, compared to other targets, at this lower dose. St-siα2reduced α-globin expression by 70%±9% (P<0.01) while Hs-siα2 generatedreductions of 80%±5% (P<0.005). Hs-siα1 remained most effective,reducing α-globin mRNA by 90%±4% (P<0.001) [FIG. 4]. At 48 hours,reductions mediated by St-siα1 were no longer significant but St-siα3appeared more effective than at 24 hours, reducing α-globin by 60%±12%(P<0.05) compared to mock electroporated cells. There were nosignificant changes in all other sequences tested compared to resultsobtained at 24 hours (FIG. 4).

EXAMPLE 6

Development of Vector Delivery System

A mono-cistronic vector is developed for the tissue-specific expressionof a short hairpin (sh)RNA from an erythroid-derived polymerase (pol) IIpromoter (FIG. 5). α-Globin-specific shRNAs are generated in erythroidcells. A Lentiviral (LV) β-globin vector (FIG. 5) is modified so that itexpresses the shRNA sequence under an erythroid-specific pol IIpromoter. This means the shRNA sequence will only be produced inerythroid cells. The LV β-globin vector is modified by insertingα-globin-specific shRNA sequences within the 5′UTR or intron 2 ofβ-globin. This also lowers the concentration shRNA sequences requiredand, therefore, possible off-target effects. Additional toxicity issuesmay also be addressed by removing the HS2 and HS3 from β-globin LCR.

Example 7 Clinical and Animal Trials

A Lentiviral (LV) β-globin gene therapy vector (LVβ) is proposed totransfer a therapeutic β-globin transgene with high efficiency andfidelity to hematopoietic stem cells in combination with RNA-mediatedsilencing to reduce α-globin production. It is proposed that thisapproach will achieve a normal range of hemoglobin (Hb) A, i.e. 14-17g/dL. Aspects covering the delivery of therapeutic β-globin aredescribed in Cavazzana-Calvo et al. (2010), Nature 467:318-322.

Hence, this trial is based on a complementary approach of limitingα-globin gene expression by RNAi in combination with a therapeuticβ-globin gene expression approach.

The LV β-globin gene therapy vector expresses a variant of normal adultβ^(A)-globin (β^(A-T87Q)) which has a therapeutic efficiency in aβ-thalassemic mouse model. The RNAi approach includes targeting α-globinmRNA at a site selected from the 5′-UTR, Exon1, Exon3, the 3′-UTR and aboundary region inbetween. In an embodiment, the RNAi approach targetsor comprises a nucleotide sequence selected from SEQ ID NO:25, 26, 27,28, 29, 30, 31 and 32.

Conveniently, the RNAi in the form of a short hairpin (sh)RNA isdelivered by Lentiviral vectors (LV). In an example Lentilox 3.7 (LL3.7)is a third generation self-inactivating (SIN) LV system (Rubinson et al.(2003), Nat. Genet 33:401-406). RNAi expression is mediated by type IIIRNA polymerase (Pol III) or type II (Pol II) transcription in the formof shRNAs.

Erythroid progenitor cells extracted from the bone marrow ofβ-thalassemic patients are cultured for 5 days in the presence of stemcell factor (SCF), dexamethasone (Dex) and erythropoietin (Epo), acombination of factors which promotes the in vitro expansion oferythroblasts. Following expansion, cells are transduced with viralvectors at a multiplicity of infection (MOI) of 1. Replacing theproliferation factors with high concentrations of Epo and insulininduces synchronous erythroid cell differentiation. Three days postviral transduction, GFP expression is used to monitor transductionefficiency and facilitate the isolation of transduced clones byfluorescent cell sorting. The efficacy of shRNA LV vectors is determinedby qRT-PCR. T RNAi LV vectors balance globin synthesis to near wild-type(WT) levels.

Restriction of RNAi delivery in a time and tissue-specific manner iscritical to minimize potentially deleterious off target effects. PolIII- or Pol II-directed intronic RNAi expression systems is used. Inthis strategy, an RNAi is encoded within an intron of a gene that isspecifically expressed in the cell type of interest. Following Pol IIIor Pol II RNA processing, some of the intron-derived dsRNA fragments canform mature miRNAs thereby silencing the target gene, while the exonsare ligated together to form mature mRNA for protein synthesis.

For therapy, the synthesis of α- and β-globin proteins must be balanced.The use of RNAi to yield a moderate reduction in α-globin in erythroidcells requires a highly specific and lineage-restricted gene-silencingvector. An erythroid-specific expression system is the LV β-globin genetherapy vector.

An example of a LV system comprises the 5′-LTR, cPPT, RRE, the β-globingene and one or more nucleic acid molecules encoding chicken globinhypersensitive sites 2, 3 and/or 4 (HS 2, 3, 4, respectively).

It is proposed to modify LVβ gene therapy vectors by insertingα-globin-specific RNAi sequences into the intronic region of theβ-globin gene. The LVβ vector is based on the design detailed above andproven successful for the correction of SCD and β-thalassemic mice butwith the incorporation of a number of modifications to reduce the riskof genotoxicity, including i) utilizing a self-inactivating (SIN) LVvector containing deletions in the LTRs, with complete removal of bothviral enhancer and promoter region, ii) use of enhancer/promoterspecific for the erythroid lineage, and iii) use of chromatin insulatorsfrom the chicken globin hypersensitive site 2, 3 and/or 4 (cHS2-4). Suchinsulator sites are well characterized in mammalian cells. The cHS4enhancer blocking activity, for example, is most effective as a doubletand this is the configuration used in the LVβ vector currently underevaluation in phase I/II clinical studies.

α-Globin-specific RNAi sequences are inserted within intron II of theβ-globin gene, thereby limiting the expression of α-globin in erythroidcells while the β-globin exons are spliced together to form mature mRNAfor protein synthesis.

A clinically approved LVβ vector is modified to enable intronic deliveryof α-globin-specific RNAi molecules. The level of silencing produced bythe α-globin-specific shRNA is sequence-dependent, which means thatsequences of variable activity can be used to fine tune α-globin levels(FIG. 6). RNAi sequences are inserted into one or more of threelocations in the second intron of the β-globin gene encoded by the LVβvector: 1) positioned near the branch point (BP), 2) inserted into the375 bp deletion breakpoint, and 3) near the splice donor site.

Limited RNAi-mediated reduction of α-globin (by 25-50%) and β-globintransgene expression is proposed to synergise restoration of the α:βglobin ratio to equal levels and restore the Hb deficit reported inseveral β-globin gene therapy studies. The therapeutic potential ofLVβ-RNAi vectors is evaluated in two β-thalassemic transplantationmodels.

Model 1: LVβ and LVβ-RNAi vectors are evaluated in intermediateβ-thalassemic mice (β-KO^(+/−)). BM cells are isolated from β-KO^(+/−)mice, transduced and transplanted into lethally irradiated β-thalassemicmice. Model 2: LVβ and LVβ-RNAi vectors are also evaluated in severeβ-thalassemic (β-KO^(−/−)) mice. Fetal liver (FL) cells are isolatedfrom β-KO^(−/−) mice at E13.5, transduced and transplanted into lethallyirradiated β-thalassemic mice.

BM and FL cells are lineage depleted using the Lineage Cell DepletionKit (Miltenyi). This procedure generally yields lineage negative (Lin⁻)stem cells at purities greater than 80%. Following in vitro stimulation,cells are transferred to retronectin-coated plates and transducedovernight with viral vectors. Cells are then harvested and 1×10⁶ cellsinjected i.v. into β-KO^(+/−) recipient mice after 1100 cGY of totalbody irradiation. As transplantation controls, up to 10 mice per controlgroup are transplanted with mock-transduced β-KO^(+/−), β-KO^(−/−) andnormal cells. Additional controls include cells transduced with LVvectors with and without an irrelevant shRNA targeting sequence.

Peripheral blood is collected at several time points following BM/FLtransplantation and globin synthesis assessed by qRT-PCR, primerextension and HPLC. Phenotypic correction is determined by FBE and ROSmeasurements. Recipient mice are euthanized 1-6 months followingtransplantation. BM, spleen, liver, and heart are harvested andsubjected to multiple analyses. Recipient mice of mock-transducedβ-KO^(−/−) FL cells are anticipated to show moribund features by day 30due to profound anemia. The degree of phenotypic correction isdetermined by measuring erythroblast (Ter-119⁺/CD71⁺) populations in theBM and spleen of treated mice. Prussian blue staining will be used toassess the level of iron deposition, which is an indirect measure ofineffective erythropoiesis. Experiments employ statistically significantnumbers of animals and the two-tailed Student's t test will be used todetermine statistical significance.

The effects of LVβ-RNAi vectors containing human α-globin-specific RNAisequences are evaluated. Peripheral blood samples are drawn from healthydonors and from β-thalassemia patients. CD34+ cells are isolated byimmunomagnetic cell separation using CD34 MicroBead kit (Miltenyi).Early erythroid progenitors are expanded, followed by synchronouserythroid differentiation. LVβ-RNAi vectors are introduced into culturedhuman erythroid progenitors and evaluated on days 1-5 following theinduction of differentiation. LVβ and LVβ-RNAi gene therapy in twogroups of β-thalassemia patients (HbE and IVS1-110 genotypes). HbE iscommon in Southeast Asia and causes 40-70% reduction of β-globinsynthesis, whereas IVS1-110 is frequently observed in southern Europeresulting in 90% reduction in β-globin synthesis. α/β-Globin synthesisis assessed by qRT-PCR and by [³H] leucine incorporation into globinchains. At least 5 HbE and 5 IVS1-110 patients are examined. As theclinical severity of β-thalassemia is influenced by the presence ofα-thalassemia or HbF production, it is necessary to confirm the presenceor absence of genetic modifiers of disease. This allows monitoring ofbalanced α-/non-α-globin synthesis in the β-thalassemia patients.

Those skilled in the art will appreciate that aspects described hereinare susceptible to variations and modifications other than thosespecifically taught. It is to be understood that these aspects includesall such variations and modifications. Aspects disclosed herein includeall of the steps, features, compositions and compounds, individually orcollectively, and any and all combinations of any two or more of thesteps or features.

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1. A method for treating a human subject with β-thalassemia or a relatedhemoglobinopathy, said method comprising administering to said subjectan effective amount of an RNA molecule which targets an mRNA speciesencoding α-globin at a site selected from the 5′ untranslated region(5′-UTR), Exon1, Exon3 and the 3′-UTR or a boundary region inbetween tothereby reduce the amount of α-globin produced to non-zero levels andameliorate the effects of an α- and β-globin chain imbalance.
 2. Themethod of claim 1 wherein the RNA comprises a nucleotide strand of fromabout 15 to about 50 bp in length.
 3. The method of claim 1 wherein theRNA is a short, interfering RNA molecule or a chemically modified ormimetic form thereof.
 4. The method of claim 3 wherein the RNA is ahairpin RNA.
 5. The method of claim 3 wherein the mimetic is a peptideoligonucleotide.
 6. The method of claim 3 wherein the chemicallymodified RNA is a branched oligonucleotide or hairpin oligonucleotide.7. The method of claim 1 wherein the level of α-globin is reduced to alevel of from about 30% to 95% of the level of α-globin in a cell from asubject not suffering from β-thalassemia.
 8. The method of claim 1wherein the RNA which targets the α-globin mRNA is expressed in a5′-UTR, 3′-UTR or intron of a nucleic acid molecule which encodes afunctional β-globin.
 9. The method of claim 1 wherein the RNA comprisesa nucleotide strand which comprises or targets a nucleotide sequenceselected from SEQ ID NO:25, 26, 27, 28, 29, 30, 31 and
 32. 10. Themethod of claim 1 wherein the related hemoglobinopathy is HbE or sicklecell disease.
 11. Use of an RNA molecule which targets an mRNA speciesencoding α-globin at a site selected from the 5′ untranslated region(5′-UTR), Exon1, Exon3 and the 3′-UTR or a boundary region inbetween andreduces the amount of α-globin produced in the manufacture of amedicament in the treatment of β-thalassemia or a relatedhemoglobinopathy in a subject.
 12. Use of claim 11 wherein the siRNAcomprises a nucleotide strand of from about 15 to 50 bp in length. 13.Use of claim 11 wherein the RNA is a short, interfering RNA molecule ora chemically modified or mimetic form thereof.
 14. Use of claim 13wherein the RNA is a hairpin RNA.
 15. Use of claim 13 wherein themimetic is a peptide oligonucleotide.
 16. Use of claim 13 wherein thechemically modified RNA is a branched oligonucleotide or hairpinoligonucleotide.
 17. Use of claim 11 wherein the RNA comprises anucleotide strand which comprises or targets a nucleotide sequenceselected from SEQ ID NO:25, 26, 27, 28, 29, 30, 31 and
 32. 18. Use ofclaim 11 wherein the related hemoglobinopathy is HbE or sickle celldisease.
 19. An isolated RNA which targets an mRNA species encodingα-globin at a site selected from the 5′ untranslated region (5′-UTR),Exon1, Exon3 and the 3′-UTR or a boundary region inbetween and whichreduces the amount of α-globin produced for use in ameliorating thesymptoms of β-thalassemia or a related hemoglobinopathy in a subject.20. The isolated RNA of claim 19 wherein the RNA comprises a nucleotidestrand of from about 15 to about 50 bp in length.
 21. The isolated RNAof claim 19 wherein the RNA is a short, interfering RNA or a chemicallymodified or mimetic form thereof.
 22. The isolated RNA of claim 21wherein the RNA is a hairpin RNA.
 23. The isolated RNA of claim 19wherein the mimetic of the RNA is a peptide oligonucleotide.
 24. Theisolated of claim 19 wherein the modified RNA is a branchedoligonucleotide.
 25. The isolated of claim 19 wherein the RNA comprisesa nucleotide strand which comprises or targets a nucleotide sequenceselected from SEQ ID NO:25, 26, 27, 28, 29, 30, 31 and
 32. 26. Theisolated RNA of claim 19 wherein the related hemoglobinopathy is HbE orsickle cell disease.
 27. The isolated RNA of any one of claims 19 to 26in a pharmaceutical composition comprising one or more pharmaceuticallyacceptable carriers and/or diluents.
 28. A vector comprising a nucleicacid molecule encoding human β-globin operably linked to a promoter anda second nucleic acid molecule inserted in the 5′-UTR, 3′-UTR and/or anintron of the β-globin nucleic acid molecule, which second nucleic acidmolecule encodes an RNA which targets an mRNA species encoding α-globinat a site selected from the 5′ untranslated region (5′-UTR), Exon1,Exon3 and the 3′-UTR or a boundary region inbetween.
 29. The vector ofclaim 28 wherein the β-globin nucleic acid is operably linked to the polII or pol III β-globin promoter.
 30. The vector of claim 28 or 29wherein the nucleic acid molecules encoding the RNA comprise or target anucleotide sequence selected from SEQ ID NO:25, 26, 27, 28, 29, 30, 31and
 32. 31. The vector of claim 28 wherein the vector is a Lentiviralvector.